Glutathione transferase (GST) is an important enzyme involve in metabolizing
many different classes of xenobiotics through conjugation with glutathione.
The hide beetle (Dermetes maculatus) is an important insect pest ravaging
agricultural stored products globally, thereby reducing their economic value.
As such, the control of this insect is necessary to enhance both quality and
quantity of stored products. This paper presents the inhibitory activity of the
ethanolic extract of cayenne pepper (Capsium annum) on purified GST from
the larvae of hide beetle. The larva were collected from decaying dried catfish
(Clarias sp), demobilized by freezing at 4 °C and homogenized with 0.1 M
phosphate buffer (pH 7.0) containing 1 mM each of ethelene diaminetetraacetic
acid (EDTA) and β-mercaptoethanol on ice. The homogenate was subjected to
cold centrifugation at 10,000 g for 20 min. The supernatant was used as the
crude enzyme solution, which was purified by ion-exchange on DEAESephacel and affinity Chromatography on glutathione-Sepharose 4B before
inhibitory studies with C. annum ethanolic extract and known plant-based
inhibitors. The concentration of C. annum extract causing fifty percent
inhibition (IC50) of GST activity was similar to that of anisaldehyde but less
potent when compared with α-terpeneol. The C. annum extract exert its
inhibitory power on the glutathione transferase via mixed inhibition. These
findings showed that GST is present in D. maculatus larvae, and the inhibitory
properties of C. annum extract can be employed in designing inhibitors with
enzymic target for pest control thereby improving quality and quantity of stored
products.
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